Merge pull request #283 from Anoven/develop

Fixing the Image operators(__add__,__sub__,__and__,__or__) for scalars.
deleted wrong comment
Fixed annoying None return instead of 0 length lists.

Here's why the previous code was a bad idea. I would expect this code to work when there's no blobs:

for blob in myimage.findBlobs():
	blob.draw()

But it doesn't when there's no blobs, instead I get something like TypeError: 'NoneType' object is not iterable.